One needs clairvoyance in order to observe the spiritual world. To understand it, only common sense and logic are necessary. Today, many people who adopt materialistic thinking to various degrees, are possessed by the delusion of infallibility – an outcome of positivism in science. The people of today live in pure fantasy and are unable to distinguish reality from illusion. Although they do not admit the infallibility of the Pope, they think of themselves as infallible. Those who adopt the scientific outlook are nowadays the most intolerant. According to them, spiritual scientists are nothing but fools…but they? Well, they are of course simply infallible ;-).
Source (German): Rudolf Steiner – GA 56 – Die Erkenntnis der Seele und des Geistes – Berlijn, November 28, 1907 (page 119)